1. Field of the Invention
This invention relates generally to routing in Internet protocol (IP) networks.
2. Description of Related Art
In computer networking, such as IP networks, and telecommunications, multi protocol label switching (MPLS) is a data-carrying mechanism that belongs to the family of packet-switched networks. MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer), and thus is often referred to as a “Layer 2.5” protocol. MPLS is designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. MPLS is used to carry many different kinds of traffic, including IP packets, as well as native asynchronous transfer mode (ATM), synchronous optical networking (SONET), and Ethernet frames.
A Pseudowire (PW) is an emulation of a native service over a Packet Switched Network (PSN). The native service may be a layer 2 or SONET connection, ATM, Frame Relay, Ethernet, low-rate time division multiplexing (TDM), or SONET/SDH, while the PSN may be MPLS, IP (either IPv4 or IPv6), or L2TPv3. More particularly, a PW is a tunnel established between two provider-edge (PE) nodes to transport Layer 2 Protocol Data Units (PDUs) across a PSN.
A multi-segmented PW (MS-PW) is one which traverses multiple PSN domains. i.e. one or more Service Provider (SP) networks, or multiple networks within the same SP network (e.g. an access and core network). More specifically a MS-PW is a static or dynamically configured set of two or more contiguous PW segments that behave and function as a single point-to-point PW. Each end of a MS-PW terminates at an Ultimate Provider Edge (U-PE) device.
The subject matter described herein pertains to routing through a network, including MPLS and MS-PW. Routing is the process of finding a suitable route for conveying data between a source and a destination. Routing can be subject to a set of constraints, such as quality of service, policy or pricing for users of routing services.
Constraint-based path computation is a strategic component of traffic engineering in MPLS networks. It is used to determine the path through the network that traffic should follow, and provides the route for each label switched path (LSP) that is set up.
Path computation has previously been performed either in a management system or at the head-end of each LSP. But path computation in large, multi-domain networks may be very complex and may require more computational power and network information than is usually available at a network element, yet may still need to be more dynamic than can be provided by a management system.
A path computation element (PCE) is defined by the Internet Engineering Task Force (EETF) as an entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints. Thus, a PCE is an entity capable of computing complex paths for a single or set of services. A PCE might be a network node, network management station, or dedicated computational platform which is aware of the network resources and has the ability to consider multiple constraints for sophisticated path computation. PCE applications include computing label switched paths for MPLS traffic engineering. Thus, PCE has a vision of networks where route computations are more or less separated from actual packet forwarding and could have a vision of a network that ignores temporary conditions, such as router or link failures, causing sub-optimal routing. It should be apparent that there is a need for systems and methods that enhance routing optimality in IP networks requiring path establishment, including those using one or more PCE.
The foregoing objects and advantages of the invention are illustrative of those that can be achieved by the various exemplary embodiments and are not intended to be exhaustive or limiting of the possible advantages which can be realized. Thus, these and other objects and advantages of the various exemplary embodiments will be apparent from the description herein or can be learned from practicing the various exemplary embodiments, both as embodied herein or as modified in view of any variation which may be apparent to those skilled in the art. Accordingly, the present invention resides in the novel methods, arrangements, combinations and improvements herein shown and described in various exemplary embodiments.